concurrently.py needs to output errors

Our current merge jobs leave a line telling people to examine the *.err.log files. The errors are not printed in the console. In addition, the *.err.log files are also the incorrect place to look as the test output happens in the *.out.log files.

We need to modify things so when errors occur, they appear in the log. In addition, let's combine the out and err logs into a single file to artifact.